For those who do not profess the faith, a life within sin is problematic spiritually, rather eternally, however, for those who are believers with Christ dwelling within, not merely identifying as Christian truly or doing so publicly, and upon doing so fall into sins, even little ones, simply of the mind: this man has or will have a life filled with tragedy, for having been graced as a king with a wealth and power and authority has turned his mind and will away from a kingdom and towards lesser things.
I speak from personal experience.
Why does the Christian, with Christ within, bear greater punishment from God? Why does his life contort to be not of heaven but of hell upon falling into sins? Should not his life be filled with love, with glory, and with honors?
The Christian has knowledge of truth, making mortal sin more possible, his knowledge a greater burden for the conscience in similar activities as those who do not possess knowledge of the truth. What would otherwise be due ignorance, is not spiritually if not even mentally a great sacrilegious act towards God, for he possesses spiritual and mental knowledge of God in possessing faith. Not only this, but in receiving the sacraments, the Christian is bolstered, supported, and has fully received many graces from God, making a fall into sin like losing a war while being equipped with more soldiers, better weaponry, and even the blessing of God.
What value is the fear of the Lord, what place must it have in our hearts now, knowing that those who receive sacraments and are blessed with living faith from God are not receiving only what is good, but what is priceless and irreplaceable, and holy beyond measure, its value being beyond compare that when wasted brings wrath and tragedy upon the Christian, to a greater degree than unbelievers, to bring him back to repentance. The greater the knowledge of God and of the truth, the greater the tragedies that inflict the Christian, the greater the punishments he must endure, for the truth was not sufficient for him to live a life of holiness.